Stiffen up deck stairs

[work sucks]

I am building a deck for a neighbor and he didn't want a landing on his stair. The rise is 10'4" and the run is about 14'. I cut 4 strigers out of 2X12 at a 7 1/4 step and 10 1/4 run. I can already tell that there is going to be a little bounce to the stair. He is willing to run HSO 2X12's on the outer two stringers for added strength, but is this going to be enough or will I also need to run 2X6 with the 2 inside stingers? Perhaps someone has a better idea on this before I throw a bunch of additional lumber at it. Thanks for the help.

[Pooh]

how wide is the stairs? 4 stringers by themselves should be plenty

[work sucks]

42" wide. I don't have it completely assembled yet, so maybe once I put the 1x12 cedar over the outside stringers (skirt) it will be a bit more rigid.

[upnorth]

Every stair tread and skirt(if I am thinking the same thing) will stiffen things up pretty good. You will literally tie the material into one solid unit.

[Surface Tension]

If the stairs are running along side the deck you can anchor the inside stringer to a post and a bracket to support the outside stringer.

Hand rails can stiffen the stairs a lot or they can just add more weight. Just pick a design that act like a truss when its tied to the stringers.

Adding 2x6 to the two center stringers won't do a lot.

The 1x12 trim would do a lot more to stiffen the stringers.

Risers will stiffen the treads and stairway.

[crothmeier]

I build a TON of decks on the side, 4 stringers on a 42" wide stairs will be plenty good. If you run the 2x2 balluters all the way down to the outside stringer that will make a huge difference. They will seem really bouncy until you get all of the components put together.

i've found its easiest to start assembly on the ground, put 3-4 treads and risers on, then get a couple guys and lift it into place, everything seems to line up better that way.

[work sucks]

Thanks all...I'll finish building it the way I initially set out. I've built them this way before and don't recall them being bouncy, guess they need to be complete before I worry.

[Marbleye'd]

I agree....they will be just fine when they are assembled. Unless the stringers have big checks or knots the size of hockey pucks. Use some pl or any other exterier glue too it will add to the strength.